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Thursday, February 26, 2009

The Obama administration has presented a summary of what will be its Fiscal Year 2010 budget. The news for NASA overall is good. The FY10 proposal will be $1.4B greater than the FY08 actual and $900M more than the FY09 proposed budget. In addition, the stimulas package provides an additional $1B, with most of those funds targetted to new Earth observation missions (my bread and butter) and to exploration, which I believes means manned exploration.

The FY10 summary is sparse on details -- the entire paragraph dealing with robotic exploration appears below. The key news is that if Congress approves the budget, then NASA will have some significant new funding. We will have to wait until this spring to see how much goes to the planetary program. My guess is that the majority of the increase will go to Earth observations and building the craft for the next generation of manned flights. However, the increased money decreases pressure on NASA to pull money from the science programs to fund the manned program. My guess is that the best the planetary program will get may be some extra money to help pay for the Mars Science Laboratory cost overruns. NASA already has a number of planetary programs in flight or underway. Just keeping those on track will, in my opinion, be good news. However, the Obama administration is welcome to delight me by proving me wrong with a significant increase to the planetary program. :>

[The proposed FY10 budget]Funds a Robust Program of Space Explorationinvolving humans and Robots.NASA’s astronauts and robotic spacecraft havebeen exploring our solar system and the universefor more than 50 years. The Agency willcreate a new chapter of this legacy as it works toreturn Americans to the Moon by 2020 as partof a robust human and robotic space explorationprogram. NASA also will send a broad suite ofrobotic missions to destinations throughout thesolar system and develop a bold new set of astronomicalobservatories to probe the mysteries ofthe universe, increasing investment in research,data analysis, and technology development insupport of these goals.

For those of you not familiar with the U.S budgeting process, here's a brief overview. The President proposes a budget for the next fiscal year (which starts Oct 1), usually in February. When there is a new administration, the details usually come in the spring. The two houses of Congress, the House of Representatives and the Senate, each pass their own version of the budget which can differ by several hundred million for NASA's science program. The two houses plus the White House then dicker on the details and pass a final budget which then must be approved and signed by the President. The final FY10 budget is unlikely much before October and may well come sometime after that.

In the past few years, Congress and the White House have not been able to agree on a budget, and NASA (along with most other branches of the U.S. government) have been funded at approximately the previous year's level. This effectively is a cut in funding since inflation will reduce purchasing power. Budget increases for NASA will be welcome, indeed.

Wednesday, February 25, 2009

The Planetary Society has posted a neat image prepared by the mission team showing all the past and planned encounters with moons for the Cassini mission. Click on the image below to go to their web site for a full size version.

Tuesday, February 24, 2009

The Cassini management has approved a mission plan for a seven year extended extended mission (XXM) -- also known as the Solstice mission -- that would continue explorations of the Saturn system until 2017. The Planetary Society has an in-depth description of the mission goals and plans. For those that want a quick summary, I'll provide one here.

Currently, the mission is in the midst of a two year extended Equinox mission. At the end of that time, the mission management expects to have healthy spacecraft that would explore for many more years.

The mission planners had a number of goals they wanted to achieve. The first was to last until the summer solstice arrives in the Saturn system to provide a complementary view to the winter season that was present when the spacecraft arrived. (A Saturnian year is 29.5 Earth years.) That would extend the mission an additional seven years beyond the end of the Equinox mission. For the Solstice mission, the planners wanted to maximize the number of encounters of Titan and Enceladus to both further the mapping of these worlds and to look for changes. At Titan the changes would be in the weather systems and at Enceladus they might be to the system of geysers. At the same time, the planners wanted to achieve as many close encounters with other moons as possible. At the end of the mission, the spacecraft needs to be disposed in a place where there will be no chance of accidental collision with and contamination of either Titan or Enceladus.

At the same time, the planners had a number of constraints. Foremost is that the spacecraft will have used four-fifths of its fuel supply by the end of its current extended mission. So the last seven years would have to get by on a quarter of the fuel that was used in the first six years. In addition, the mission will have to be done with less money a year than it currently spends ($80M/year). The Planetary Society blog doesn't list say what the new budget will be.

The mission that the planners came up with promises to be exciting with 56 flybys of Titan, 12 of Enceladus, three of Dione, 20 orbits that pass just outside main rings, and a final 23 orbits that pass inside the ring system just above the cloud tops of Saturn. (These are just the highlights -- many other observations would be carried out in addition to these encounters.) In the last phase of the mission, Cassini will be able to replicate the magnetosphere and gravity measurements that the Juno mission will do at Jupiter. (Cassini lacks the instruments that Juno will carry to look deep into Saturn's atmosphere.) At the end of the mission, Cassini's fuel should be all but gone, the spacecraft will be set on a course to plunge into Saturn's atmosphere.

The Solstice mission still needs to be approved, especially the end of the mission plan to dispose of the orbiter into Saturn. The cost of the mission also will not be trivial. Apparently the mission management looked at trying to get by with $40M a year, but that apparently was too tight. Let's say that the mission can be done for $60M a year. Over the course of the seven years, the cost almost will equal the cost of doing a Discovery mission. For myself, this would represent a bargain. I have trouble conceiving of any other mission that could return the science and awe of the Solstice mission for the money that would be spent.

Final close up orbits just above Saturn's clouds. Click on the image or here to go to a presentation on the options considered and science goals of the Solstice mission. The discussion of the science goals starts about the middle of the presentation.

Jason Perry has been exploring the views that Cassini would have of several of the moons during the Solstice mission, and he has provided the following examples and captions:

Despite the fact that Cassini will be flying by Titan 56 times during the XXM, my favorite Titan encounters is actually a non-targeted one on July 10, 2017. This encounter willprovide our best opportunity to image Kraken Mare at excellent emission angles. The XXM mission will provide scientists with an opportunity to monitor Titan's polar lakes.

Cassini's 12 flybys of Enceladus will provide opportunities to monitor the south polar plumes using several 50 km encounters of the south pole, high-resolution mapping of the north polar region, and stereo coverage.

Cassini will fly by Dione three times during the extended mission, including one encounter in December 2011 that will take the spacecraft over a set of unusual pits that may have a cryovolcanic origin on the moon's leading hemisphere.

Jason Perry asked where the funding for Cassini was in the budget I posted in the previous blog entry. The proposed document I looked at didn't discuss Cassini at all. I went back to the original Bush administration FY09 budget and found, "Cassini has been transferred to the Outer Planets Program." This would mean that a substantial portion of the money I "projected" from that line item to future mission development would not be available for building future planetary craft.

I want to re-emphasize that the budget analysis was not meant to be precise -- almost all the guesstimates for future mission costs, for example, are certainly wrong in the details.

Rather, the message is that while $1.3B per year for planetary exploration seems like a large amount, it does not allow for lots of new missions to be added to the roadmap in the coming decade. Running out existing programs and plans likely will use up available funds unless Congress appropriates a larger budget.

Monday, February 23, 2009

Jason Perry asked where the funding for Cassini was in the budget I posted below. The proposed document I looked at didn't discuss Cassini at all. I went back to the original Bush administration FY09 budget and found, "Cassini has been transferred to the Outer Planets Program." This would mean that a substantial portion of the money I "projected" from that line item to future mission development would not be available for building future planetary craft.

I want to re-emphasize that the budget analysis was not meant to be precise -- almost all the guesstimates for future mission costs, for example, are certainly wrong in the details.

Rather, the message is that while $1.3B per year for planetary exploration seems like a large amount, it does not allow for lots of new missions to be added to the roadmap in the coming decade. Running out existing programs and plans likely will use up available funds unless Congress appropriates a larger budget.

Original Post

In this blog entry, I'll look at the types of planetary missions that NASA may be able to develop in the coming decade. I'll start with a proposed budget for this current Fiscal Year (FY09) and extrapolate into the future with some educated swag costs of potential missions.

All figures presented here come from a proposed (not passed) House budget for FY09, which means that many of the specific numbers will change before it becomes law. If you are so inclined, the proposed budget figures can be found buried here. If I understand ESA's budget correctly, it spends about 434M euro (~$555M) for its entire science budget (not including another 585M euro for Earth observations). (ESA's budget figures are not directly comparable to NASA's because ESA's member nations pay for the development of scientific instruments outside of the ESA budget. Science instruments are not a trivial expense, and this likely adds tens of millions of euros to ESA's effective budget.)

What does all this mean for future NASA planetary exploration?

First of all, it is instructional to look at the top line, which is approximately $1.33B for FY09 to development new missions, operating in-flight missions, analyze data from on-going and past missions, and develop new technology for future missions. The development of new missions gets ~$752M or ~57% of the budget and everything else gets ~$575M or ~43% of the budget. That second, "everything else" category is a big bucket of money. When you hear of NASA trying to save money by reducing mission operations for missions past their prime mission, it is because dollars spent on old missions can't be spent for future missions.

Where is the money for future mission development budgeted to go? Here is what's in the proposed budget:

If I understand the implications of the Mars Science Laboratory (MSL) slip, a good chunk of the outer planet mission money may go to fund the MSL cost overruns. That would be one of the reasons that the Jupiter Europa Orbiter is planned for lauch 11 year hence.

The current fiscal year is merely a snapshot in time. What is perhaps more interesting is to look at what budgets like this might mean for planetary mission development over the next decade. For this exercise, I'll assume that future budgets, adjust for inflation, are approximately the same as current budgets. I'll also make some guesstimates about what several categories of proposed missions would cost in FY09 dollars (an exercise where I'm bound to be wrong in the specifics because the figures I've seen quoted have assumed wildly different base FY years).

If NASA is spending $752M a year to develop new missions, what can it afford over the course of the next decade? Here is one possible breakdown, with assumptions for three Discovery and two New Frontiers missions:

Click in image for larger view. Dollars in $1,000s.

(New Frontiers costs assume $650M for the spacecraft and $100M for the launch vehicle, with the latter a swag.)

As I've said, the details are certainly wrong here. NASA can also decide to change how it allocates money (for example, do fewer Discovery missions to beef up the Mars program). So take this as an example of one possible roadmap constrained by approximately current spending levels. If my analysis has any validity, this allocation of mission development funds seems to mean is that NASA may already be committed to its major planetary mission roadmap for the next decade

- Its Principle Investigator-led missions (Discovery and New Frontiers)

- A Mars program consisting of MSL, ExoMars contribution, and one medium sized mission

- The Jupiter Europa Mission.

It will be interesting to see if the Decadal Survey in progress to plan the roadmap for the next decade will hold to these priorities.

Here is the Planetary Science budget from the proposed FY09 budget referenced above:

The current issue of Aviation Week and Space Technology (2/23) has a few tidbits that I haven't seen elsewhere that I'll pass along.

The key issue with the Titan Saturn mission was the the concept was less mature than for the Jupiter Europa mission. The reviewers were concerned about details of the engineering proposal, the propulsion system, and trajectory. They also felt that the mass margins were too small to handle possible increases in mass that could have caused it to be unable to be launched with its stated launch vehicle. The article doesn't say whether there is a launch vehicle with the mass margin that would be too expensive or if there simply wouldn't be a good alternative.

NASA is reviewing whether or not to use Advanced Stirling Radioisotope Generators (ASRGs) in place of the plan of record Multimission Radioisotope Thermoelectric Generators (MMRTG). ASRGs would use a fraction of the plutonium of the MMRTGs, potentially leaving enough in NASA's stockpiles to fuel other (especially smaller missions of New Frontiers or Discovery class) missions. The key issue whether the ASRGs could be validated in time, particularly since they have moving parts that cycle 100 times per second and must do so reliably for 15 years.

ESA will decide between its Jupiter Ganymede orbiter and two astronomy missions (the International Interferometer Space Antenna and the Laser Interferometer Space Antenna) in 2011. (Another competitor that would study dark matter/energy in the universe was withdrawn from the competition when ESA decided to pool that effort with a U.S. effort.)

NASA plans to continue to study Titan missions to be ready to proceed should the Decadal Survey make a mission to return to Titan a priority.

One of my favorites, the Saturn Ring Observer would have a craft hover over the rings for detailed observations. Several methods have been proposed to bring the craft into orbit around Saturn at a distance where the craft is just a kilometer or two above the rings. The craft's engines would fire every so often to keep it safely above the rings. From there, it would provide "to obtain close-in observations of centimeter-scale ring particle interactions"[emphasis added] to determine the mechanics of ring collisions. The results could give insights into how planets and moons formed from rings of material in the early solar system.

To put this mission proposal into context, JPL has a small team that looks a decade or two out to envision possible planetary missions. They develop concepts for possible planetary missions and works out the engineering requirements and the new technologies that would be required. So far as I know, the Saturn Ring Observer is not on any space agency's mission roadmap. Several technologies (including aerocapture) probably would need to be developed.

Portree's website can also be thought of as a historical analysis. Regular readers of my blog may have noticed a degree of cynicism about the probability of a Mars Sample Return (MSR). Portree documents the history of proposals for this mission, none of which as ever been approved for flight, much less left the ground. These missions have been studied since I was in junior high. I have a feeling that they may still be being studied when my grandchildren (and my son is only 19 with no romantic interests he's told his parents about) are in junior high. This mission is technically tough (and maybe beyond our technology given current launch vehicles) and expensive. The cheapest recent guesstimate I've seen is ~$3B and the smart money seems to be on $5-6B.

Thursday, February 19, 2009

One of the readers of this blog sent me a note asking why it will take almost 11 years to launch the just selected Jupiter Europa Orbiter (JEO) mission. I have not followed all the ins and outs of this, but I'll share what I think I understand. Normally, a new mission takes approximately four years to develop after it receives a new mission start. Prior to that, it is common to spend some time in pre-start mission development. If money was no issue, it would be reasonable to expect that JEO would launch in the mid 2010s. A 2007 study of a Europa Explorer (the predecessor concept to JEO) presumed the launch would be in 2015. If you look at NASA's expectation for launching the Flagship mission a year ago, the target date was 2016-2017.

After that time, NASA slipped the launch date to around 2020. The stated reason was to align NASA's schedule with ESA's schedule, which could not fit a launch before that into its funding profile. I suspect that the looming cost overruns of the Mars Science Laboratory might have made the delay on NASA's side inevitable. In any case, now that the MSL cost overrun is on the books, funding for preliminary studies of JEO are slim for the next couple of years. So, we have a 5 year push out in expected launch date over the last two years.

Could NASA pull in the JEO schedule if ESA does not select its potential contribution, the Jupiter Ganymede Orbiter (JGO) in 2011 to fly? Potentially. However, I suspect that it will take awhile for NASA to work through the problems created by the MSL slip and the earliest launch probably would be in the 2018 timeframe at best. Without access to NASA's funding expectations, this is speculation, however.

On another topic, what if ESA doesn't select JGO? How might the JEO mission change? The major loss from JGO would be the intense set of flybys of Callisto and the study of Ganymede from orbit about that moon. JEO has an excellent set of instruments for studying the moons of Jupiter during flybys. In fact, a series of flybys are planned of all four Galilean moons. JEO cannot carry enough fuel to orbit Ganymede as well as Europa, so the study of Ganymede from an orbiter would be lost. On the other hand, JEO could delay its orbit insertion at Europa to allow more time for more flybys of other moons. (More flybys than the planned handful at Io are probably out because of radiation issues.) JGO would spend approximately a year conducting 19 flybys of Callisto. JEO could spend an additional year carrying out flybys of either Callisto, Ganymede, or both. If such a plan was implemented, I would expect Ganymede to receive the lion's share of additional study. The scientific community has prioritized further study of Ganymede over Callisto.

Jason Perry has posted another excellent analysis on his website about what the selection of JEO with its planned Io flybys would mean for the proposed Io Volcano Observer (IVO). He correctly points out that IVO would conduct more flybys (at least 7, probably 14, and possibly even more) compared to JEO's 4. The flyby geometry selected for IVO would also be more optimised than JEO would be have. (JEO will use the Io flybys in part ot set up later encounters with other moons and hence is constrained in the selection of flyby geometries.) Jason points out that the proposed IVO instrumentation would be more optimized for Io studies than the proposed JEO instrumentation would be for Io. However, this may not remain the case. The proposed instrumentation for JEO is a strawman to show capabilities and allow conceptual design of the orbiter. The actual instruments will be selected from proposals submitted by scientists in several years time. It is very possible that the winning instruments will be tuned to do better at Io than the current strawman payload would.

Two missions to the Jovian system are on the official list for the next New Frontiers mission ($650M). One is an Io observer and the other a Ganymede observer. The selection of JEO and possibly JGO would seem to make the selection of the Ganymede observer unlikely in my opinion. JGO is the Ganymede observer done right. The Io observer faces hurdles in terms of being selected, too. As Jason points out, there are still valid reasons to fly IVO. The science it would return over what JEO will and may return has to be better (and at lower risk) than the science from all other proposed missions. That may not be possible. I would love to see IVO fly, but I have strong doubts that it will. (Note: IVO is a Discovery mission ($450M) and not a New Frontiers mission. However, I think this reasoning still applies.)

As my final thoughts, I'll speculate on what may be a crowded place the Jovian system could be in the 2020s. This year (2009) is the year of the moon with Chinese, Japanese, Indian missions there now. ESA just finished a lunar mission and NASA will launch its soon (with more to come). The 2020s could be the decade of Jupiter. NASA and ESA may have orbiters exploring the moons and observing Jupiter itself. The Japanese space agency, JAXA, is considering an orbiter to explore the Jovian magnetosphere. Russia is considering a lander for Europa. Other nations likely will have the capability to send missions to Jupiter. What might those craft do? Additional craft to explore the magnetosphere would be useful. A craft in polar orbit around Jupiter could study the polar regions of Jupiter, keep an eye on Io, and explore another corner of the magnetosphere.

Unless new news comes out about JEO, I'll take a break from this topic for a bit. In the next few weeks, the NASA FY10 budget will be released and will show the new administration's priorities for planetary exploration. There will be meetings of NASA's scientific advisory boards for Venus where a Flagship mission will be proposed, the Outer Planets where we may learn more about the issues that led the selection of Europa Jupiter over Titan Saturn, and Mars where replanning the exploration roadmap for the next decade will begin. I also want to complete the discussion of concepts for missions for the next New Frontiers mission selection.

We may know within the next few years thanks to the Kepler mission, which is due to launch in early March. This mission will watch more than 100,000 stars like our own to look for dips in their light from planets passing in front of them. One line of thinking suggests that there may be millions of Earth-like planets in our galaxy.

Wednesday, February 18, 2009

A couple of people have noticed that the voting on this blog for your choice of Flagship mission ended just a couple of hours after the selection was made. Voting was opened early last fall. One reader wondered if I had some inside track. Unfortunately, I just got lucky...

The journal Nature has an article about how the collision of two satellites recently in Earth orbit could cause the upcoming Hubble service mission to be canceled. The threat to the shuttle from debris in orbit was already on the edge -- 1 in 185 -- for shuttle safety. Now that hundreds to thousands of new pieces of debris are in similar orbits the risk to the mission has increased.

If the service mission is canceled, then the useful lifetime of Hubble will be short.

The debris also threaten the many Earth observing satellites in what is knows as the A-train (afternoon equatorial crossing).

NASA and ESA have decided to pursue the Europa Jupiter and Ganymede Jupiter missions for the late 2010's Flagship mission. Per the announcement, the Titan Saturn mission had "several technical challenges requiring significant study and technology development," whereas the Jovian system missions were judged ready to fly.

Summary of Announcement

Here are several key paragraphs from the announcement that summarize the decision:

"At a meeting in Washington last week, National Aeronautics and Space Administration and European Space Agency officials decided to continue pursuing studies of a mission to Jupiter and its four largest moons, and to plan for another potential mission to visit Saturn's largest moon Titan and Enceladus.

"NASA and ESA engineers and scientists carefully studied both potential missions in preparation for last week's meeting. Based on these and other studies as well as stringent independent assessment reviews, NASA and ESA agreed that the Europa Jupiter System Mission, called Laplace in Europe, was the most technically feasible to do first. However, ESA's Solar System Working Group concluded the scientific merits of this mission and a Titan Saturn System Mission could not be separated. The group recommended, and NASA agreed, that both missions should move forward for further study and implementation.

"The decision means a win, win situation for all parties involved," said Ed Weiler, associate administrator for NASA's Science Mission Directorate in Washington. "Although the Jupiter system mission has been chosen to proceed to an earlier flight opportunity, a Saturn system mission clearly remains a high priority for the science community."

"The Europa Jupiter System Mission would use two robotic orbiters to conduct unprecedentedly detailed studies of the giant gaseous planet Jupiter and its moons Io, Europa, Ganymede and Callisto. NASA would build one orbiter, initially named Jupiter Europa. ESA would build the other orbiter, initially named Jupiter Ganymede. The probes would launch in 2020 on two separate launch vehicles from different launch sites. The orbiters would reach the Jupiter system in 2026 and spend at least three years conducting research.

"The Titan Saturn System Mission would consist of a NASA orbiter and an ESA lander and research balloon. The complex mission faces several technical challenges requiring significant study and technology development. NASA will continue studying and developing those technologies. Future work also will provide important input into the next Planetary Science Decadal Survey by the National Research Council of the U.S. National Academy of Sciences, which will serve as a roadmap for new NASA planetary missions to begin after 2013. On the European side, the interested community of scientists will have to re-submit the Titan mission at the next opportunity for mission proposals in the Cosmic Vision programme in the years to come."

My Thoughts

I am not surprised by this decision. A Europa mission has been intensely studied and technology to handle the radiation has been developed for over a decade now. Technically and programmatically, the Jovian system mission has been ready for a number of years. The Titan proposal has just a couple of years worth of analysis and technology study.

If I understand the process, this announcement puts the Europa Jupiter orbiter firmly on NASA's roadmap (subject as always to future Congressional appropriations of money). The ESA craft, though, is in competition with other good missions for a slot in the next Cosmic Visions selection in 2011 and may not be selected.

A future Titan mission, if it is a flagship class (>$3B) would presumably be in competition for a 2020's new start. It will need to compete against a Mars flagship mission (such as a sophisticated rover or a sample return) and a Venus mission. Other strong mission concepts may appear in the next decade, too.

A study done a couple of years ago found that the lowest cost for a meaningful return mission to Titan would be $1.5-2B (FY 2007 dollars, I believe) for a craft that would be multi-flyby Saturn orbiter. For around the same amount, a balloon that would directly communicate with Earth could be done (with much less data returned than would have been done with the Flagship mission). I would like to see the space agencies challenge its engineers to see what they could do to reduce this cost.

I am currently in my young 50s. When the Jovian mission(s) arrive, I will be in my young 70s. I very much would like to see a return to Saturn in my lifetime.

Monday, February 16, 2009

ESA has posted their Titan in-situ elements study assessment. This document has a wealth of detailed information on the two (and possibly three) craft that would enter Titan's atmosphere. The total package includes a balloon (termed by its French name, Montgolfière), an atmospheric probe that will land on the surface of lake, and possibly a long-lived lander (more on this later).

(Before I continue on possible Titan exploration, be sure to check out Jason Perry's description of the studies that would be performed of the thickness of Europa's ice shell by the competing Europa Jupiter mission.)

I suspect that most of the readers of this blog (and thanks to every one of the 1,390 of you who have visited since I figured out how to track this in early December) are most interested in planetary exploration for the excitement of the exploration. The Titan in-situ craft would, I believe, provide the most exciting exploration opportunity of the next twenty years. (Although the flyby of the Pluto system and future Mars rovers will be close contenders and may win out in some readers' opinion). Imagine the images captured from a Montgolfière of river beds, mountains, dune fields of a world that possesses many of the processes found on Earth -- just the deep freeze version. Think about the images captured by the lake lander as it floats gently (one hopes) on the waves of an alien see.

The day before the poll on this site closes, the Titan Saturn mission is out voting the Europa Jupiter mission by almost three to one. Given that the science is absolutely outstanding for both Flagship contenders, the landslide probably comes from the expected thrill of exploration that the in situ elements offer.

However, space agencies don't fly multi-billion dollar/euro missions only to indulge the public's desire for exploration. There has to be solid science to be performed. The study assessment lists ten firsts that the Montgolfière and lake lander would perform. I can't improve on their writing, so I'll simply copy their list here and encourage you to go through the document for more detail:

"1. First direct in situ exploration of the northern seas of Titan—the only known surface seas inthe solar system beyond Earth.2. Detailed images of thousands of kilometers of Titan terrain, with image quality comparableto that of Huygens during its descent will test the extent of fluvial erosion on Titan atHuygens spatial scales, well matched to the scales mapped globally by the orbiter.3. First analysis of the detailed sedimentary record of organic deposits and crustal ice geologyon Titan, including the search for porous environments (“caverns measureless to man”)hinted at by Cassini on Xanadu.4. Direct test through in situ meteorological measurements of whether the large lakes and seascontrol the global methane humidity—key to the methane cycle.5. First in situ sampling of the winter polar environment on Titan—vastly different from theequatorial atmosphere explored by Huygens.6. Compositional mapping of the surface at scales sufficient to identify materials deposited byfluvial, aeolian, tectonic, impact, and/or cryo-volcanic processes.7. First search for a permanent magnetic field unimpeded by Titan's ionosphere.8. First direct search for a subsurface water ocean suggested by Cassini.9. First direct, prolonged exploration of Titan’s complex lower atmosphere winds.10. Exploration of the complex organic chemistry in the lower atmosphere and surface liquidreservoirs discovered at high latitudes by Cassini."

I'll close with some interesting facts I gleamed from going through the study:

The Montgolfière will have three wide angle cameras. Two will point toward the surface for multispectral stereo imaging at <10 meter/pixel resolution. The third will look sideways for meteorological observations. A high resolution camera also will look toward the surface to provide <1 meter/pixel resolution.

The Montgolfière's ice penetrating radar will probe the surface to depths of a few hundred meters to approximately a kilometer. This will be deep enough to study near surface stratigraphy and search for subsurface bodies of liquids. It would not probe deeply enough to detect the large subterranean ocean believed to lie at some depth below the surface.

The lake lander will include a sonar to measure the depth of the lake (really, a small sea) beneath is splash point.

The study's engineers have figured out a way to potentially include a long lived lander (alas, no camera). There is some spare room and mass in the Montgolfière's entry system. By filling this space with a small radioisotopic power system, and a small (2.6 kg) package of instruments, long term (goal of > 150 days) studies of tidal distortion and rotational state, seismic, and variations in the magnetic field could be conducted. Following the deployment of the Montgolfière, the entry shield with the surface package attached would simply desend through the atmosphere to a soft landing. This lander has not been a thoroughly studied as the Montgolfière and lake lander and so isn't yet formally part of the proposal. It would be further studied if Titan is chosen as the destination for the next Flagship mission.

Sunday, February 15, 2009

The Titan Saturn System Mission (TSSM) flagship proposal has received considerable attention both at this blog and many other places. There are now over 600 pages of detailed mission description covering the orbiter and the Titan balloon and lander as well as a 39 page summary of both (available at http://opfm.jpl.nasa.gov/library/ and http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=44185#). (The balloon is more correctly termed the 'montgolfière'.) If you are not familiar with this mission, this site offers an overview (click on the submenu at the left for more detail)

In my previous entry on this mission, I talked about how focused the orbiter's instrument set are on exploring Titan itself. Many flagship missions (for example the Cassini Saturn orbiter) attempt to cover a breadth of science at their destinations. This mission is carefully focused on Titan. Every instrument appears to have been justified in terms of extending our knowledge of that moon.

On the other hand, the orbiter will spend 24 months in orbit around Saturn prior to Titan orbit insertion. What science can it conduct along the journey?

The principle target will be the tiny moon Enceladus with seven flybys. Since the discovery of its active geysers and increasing hints that they may originate in a subterrainean ocean, this moon has been a target for a follow on mission. While the TSSM orbiter's instruments will be selected for Titan science, it is fortuitous that they will also provide excellent science at this moon. Several key goals are forseen:

- High resolution imaging of the moon for both mapping and spectrometry to determine surface composition- Probing the interior of the moon down to 50 km depth with an ice penetrating radar and measuring the internal structure through analysis of the gravity field- Directly sampling the material in the geysers with a mass spectrometer that can determine the composition of molecules, including organic molecules, that are much heavier and more complext in their composition than the instruments on Cassini could

Each flyby of Enceladus will produce approximately 15Gbits of data. If all goes according to plan, we may learn whether Enceladus has an internal ocean laced with complex organic molecules that could suggest pre-biotic chemistry or even life. Among the goals of the flybys is to identify potential landing sites for a follow on mission.

In addition to flybys of Enceladus, the orbiter will fly close to Saturn's rings during its orbit insertion about that giant planet. It will come three to four times closer than Cassini to the B and C rings and seven times closer to the A ring. In addition, while Cassini passed by the rings on their unlit side, the TSSM orbiter will pass over them on the sunlit side. This will provide new opportunities to take images and perform spectrometry of the rings at resolutions better than Cassini.

For Saturn itself, the TSSM orbiter's instruments can see further into the infrared than Cassini, allowing the cameras to study atmospheric phenomena deeper than those Cassini could see. It is also possible that the orbiter may perform a small number of close flybys of other small moons in the Saturn system. If this occurs, then the ice penetrating radar would provide our first internal probes of those worlds, along with new imaging and spectral measurements of their surface.

The orbiter will also perform 16 Titan flybys before entering orbit around that world with eight at altitudes of 720 to 1240 km. Priority will be given to remote imaging and spectral measurements of the atmosphere and surface along with in situ sampling the atmosphere's tenous upper atmosphere and fields and particles. One instrument that won't be used will be the surface penetrating radar. There is concern that this instrument's deployed 10 m antenna could cause problems during later aerobraking at Titan. So that this doesn't occur, one set of antennas will be used at Enceladus and then jestissoned with the second set deployed after achieving final Titan orbit. No deployed antenna will be available for the low Titan flybys.

The planning documents unfortunately do not give details on how much of Titan will be imaged and at what resolutions during the flybys. However, a total of ~26Gbits of data would be collected.

The information provided on the Titan flybys gives hints for an alternative mission to Titan if the Titan flagship mission is not selected. NASA's scientific advisory boards have given high priority to Io and Ganymede observer missions that would study those targets during a series of flybys during an orbital tour of Jupiter. The science returned by either observer would be much less than that provided by a dedicated orbiter such as the Europa or Ganymede orbiters in the competing flagship proposal. However, if repeated flybys of those moons would be scientifically valuable, then why not for Titan? Yes, the science returned would be far less than from the TSSM orbiter. If it's flybys or nothing, though, a Titan observer may receive sufficient priority to be the next mission to this moon. The TSSM orbiter would perform 16 flybys, but the number of flybys could be much greater for an observer mission. And one could hope that a design could be found that would allow for deployed antennas during the flybys for an ice penetrating radar on such a mission. It is possible that another space agency could launch one or more balloons or landers to Titan timed to arrive when the Titan observer could act as a data relay.

One major issue for a Titan oberserver is that missions to Saturn cost more than to Jupiter -- it takes longer to reach and return the same amount of data from Saturn as Titan requires a heftier communications system and power system. A study of an equivalent Enceladus or Titan observer found that the cost would be $1.5-2B (FY 06 dollars) versus a potential cost of $650M + launcher (accounted for separately) an Io or Ganymede observer. With a $2.5B* (FY 07 dollars) cost for the TSSM orbiter, it may not be worthwhile to mount a Titan observer. On the other hand, if it is an observer or nothing to Titan for the next 20 years, one can hope that clever solutions in the $1-1.5B range might be developed. Several Mars missions in that price range are under discussion for the coming decade, so that scale of mission might be possible. Perhaps the observer is a pipe dream, but I for one will hold out hope should the TSSM mission not be selected. (And I will hold out hope for a Jovian icy moons observer if the Europa Jupiter flagship mission is not selected.)

Saturday, February 14, 2009

The final Europa and Titan orbiter proposals have been on-line for several days now. (I apologize for my slow response, but am working against a deadline for a paper of my own.) These massive (400+ pages each) tomes provide an incredible wealth of detail for both missions. Both documents, however, focus only on the NASA orbiters -- the ESA documents describing their possible contribution are still to be posted. (However, summaries of the full missions from both agencies are also available at the same web address.)

As I write this, the heads of the planetary programs for both agencies should have met on Feb. 12 (no word if they did or not). As I understand the process, they may have selected the target. If, however, no technical or cost issues ruled out one of the missions and the science upon review were equally compelling, the agencies may ask their scientific advisory boards for help in selecting the target.

The final documents are so detailed that trying to summarize them in a blog entry is virtually impossible. Jason Perry at The Gish Bar times as handled this problem by focusing on the studies the Europa orbiter would do in a series of Io flybys and the science that could be done at Io with the ground penetrating radar. I'll take a similar tact and focus just on a few highlights of the Titan orbiter mission that I found especially intriguing.

What I found most intriguing about the Titan orbiter is how tightly focused the mission is. Just six instruments are included in the payload, and each it tightly tied to science goals at Titan (although they fortunately would also greatly advance our knowledge of Enceladus during a campaign of flybys of that moon).

Two of the instruments focus on the Titan surface and subsurface:

The High-Resolution Imager and Spectrometer (HiRIS) would map Titan at 50 m resolution in three near and mid-infrared channels (2.0, 2.7, and 5 μm) where windows are present that allow clear views of the surface. This resolution is an order of magnitude better resolution than that achieved by Cassini's radar imager. (An imaging radar instrument was not selected for this mission proposal because the high orbit (1500 km) required to clear the atmosphere would have required a massive instrument with unacceptable power and data requirements.) HiRIS will also map the surface at 250 m resolution in three ranges of spectral bands to examine its composition (0.85-1.75, 1.9-2.2, and 4.8-5.8 5 μm).

The descriptions of these two instruments show how difficult the study of Titan's surface and subsurface are. The thick, aerosol laden atmosphere is clear only in specific spectral bands. The depth of the atmosphere requires that the orbiter study Titan from a height of 1500 km, limiting the capabilities of both HiRIS and the radar. Contrast that with the Europan orbiter which would achieve resolution at Europa of 1 m with its camera and penetration of the surface to 30 km with its radar from an orbit of 100 km.

For three instruments, however, the thick atmosphere of Titan allows detailed study:

The Polymer Mass Spectrometer would directly sample the atmosphere during flybys and aerobraking to determine the composition of molecules much more complex than those that Cassini could measure.

The Sub-millimeter Spectrometer would study winds and abundance of carbon dioxide and nitrile in the atmosphere from 200-1000km.

The Thermal Infrared Spectrometer would study composition and temperature of the atmosphere in the 30 - 500 km range.

Two additional science instruments round out the orbiter's compliment:

MAPP is a four instrument suite that would study the magnetosphere and plasma environment of Titan and Saturn the the coupling between their realms

The Radio Science and Acceleromter instrument would study the temperature profile of Titan's stratosphere and troposphere and its gravity field.

What are absent from this list are instruments that might be desired to study other aspects of the Saturn system. This is a carefully focused mission. That is not to say that these instruments could not advance our knowledge of other aspects of the Saturn system. Studies that this craft could do of other aspects of the Saturn system will be the subject of the next blog entry.

The Washington Post has an article on the problems of the Mars Science Laboratory. The most interesting quote is reproduced below, otherwise, I don't there's a lot new here for regular readers of this blog.

What I found more interesting were the comments on NASA Watch about the MSL problems. Most are thoughtful, and several points of view are present.

The best quote from the WP article: "Richard Cook, the project manager, said that in calculating the cost and the amount of time necessary for designing the mission, 'we didn't extrapolate how much more complex it was' than the Spirit and Opportunity mission."

Editorial comments: I have been involved with multi-hundreds of millions of dollars private industry technology development programs. Based on that experience, what I see with MSL is nothing new -- it seems to be a rule of human nature that we can't extrapolate effort required for programs that are significantly more complicated than their predecessors. (And it's not fun being the one to explain to customers who've already invested their R&D dollars based on your schedule that, hmmm, we're having a big slip.)

In the Washington Post article, Alan Stern is quoted as saying, "We need to go to a strategy where we can access Mars frequently and take advantage of what we've already invented." After having been burned myself in cost-overuns and schedule slips of technology development I find that I have developed a liking for incrementalism. I think we could have advanced our knowledge of Mars significantly without taking on the risk of MSL.

However, smart people disagree with me (and some of them actually got to make this decision). There is also an argument that along with science one of NASA's missions is to develop new technology. If big technology missions are going to be undertaken, what is the best way to do so so they don't eat the budget? Based on my experience (and please comment if your experience leads you to a different conclusion), I throw out two ideas:

1) Could the design phase have been significantly lengthened so that the full scope of the design effort could have been better known. MSL received its formal go-ahead in September 2006 (although I'm sure a lot of work had already been done) for a 2009 launch. An alternative would have been to keep the same start date but plan from the beginning to launch in 2011 and use the extra time to better identify problems. In the Planetary Sciences Subcommittee reviewing the MSL slip, someone asked how the Juno Jupiter mission development was doing. The answer was that it was rock solid because, thanks to a schedule replan, the upfront design period had been much longer than normal.

2) Perhaps we could recognize that big development efforts are likely to slip and create a budet item for them. If the planetary program can afford (to pick an arbitrary figure) $300M a year to put towards Flagship missions, then spend that much. If the mission requires more than intially planned, delay the launch and use the money from this line item.

I am a fan of MSL and excited to think of what we will learn. I think that the knowledge and exploration will be worth the investment. I just wonder if we can change the rules of the game for these big missions so that the impact on the rest of the program is less.

Tuesday, February 10, 2009

The journal Nature has published an article on a planned private lunar lander effort called Odyssey Moon. Its business plan is to deliver payloads to the moon for scientific or commercial customers. The three booked payloads are a Dutch laser-based spectrometer instrument, an experimental communications instrument, and, apparently, cremated remains. Odyssey Moon is also vying for the $20M Google Lunar X Prize.

Many of the readers of this blog know of Alan Stern who was formerly head of NASA space science directorate. He is science director for this venture as well as remaining principle investigator for the New Horizons Pluto mission.

Editorial note: I think that this is a neat concept. If the company delivers a payload to the moon, it will show how far space technology has advanced. Hmm, I wonder if they could put wheels on the lander to have a rover? I'd also love to see the concept eventually extended to missions to near Earth asteroids. As I said in a previous post, exploring the variety of asteroid types will allow us to compare and contrast the processes that formed them.

Even without these embellishments, count me as an enthusiastic supporter. I think there are many, many lunar (and maybe planetary) experiments that could make sense if the cost of delivering the instrument could be kept low enough. A small company could be the vehicle for making this possible.

For now, reaching the moon as a commercial enterprise would be a tremendous achievement, and one that would show the maturity of the space age. Ultimately, I suspect that the commercial success of the company will still depend on the willingness of governments (and many probably could afford to play at the prices suggested by the article) to fund scientists to build and launch payloads. At these costs, there is no reason that many inexpensive missions couldn't be funded. But perhaps I am too much the skeptic, and there is a commercial market out there, too.

Saturday, February 7, 2009

Comets and asteroids have been an on-going priority for planetary exploration for some time because of the clues they hold for the formation of the solar system. A number of missions have flown past or orbited these worlds and returned dust samples from a comet. Two sophisticated missions are on their way to rendezvous and land on a comet nucleus (Rosetta) and orbit two of the three largest asteroids (Dawn). In addition, two spacecraft are on their way to fly past comets. The Japanese Hayabusa craft is returning to Earth and may bring with it samples from a comet. The Russians are preparing their Phobos-Grunt spacecraft to return samples from that small moonlet of Mars.

So, what is next for the exploration of these small bodies? NASA's advisory boards set mission priorities only for the largest mission classes. (The smallest class missions in the Discovery program are selected from proposals submitted for each competition without prior prioritization of missions.) There are no plans that I am aware of for a large mission ($1-3B range). For the medium mission class, the scientific community has included three small bodies missions in its list of eight mission priorities:

Comet surface sample return to return unaltered dust and ice to Earth for thorough chemical analysis and expected breakthroughs in our understanding of the early history of our solar system

A Trojan/Centaur asteroid reconnaissance mission that would flyby or orbit one of these outer solar system classes of asteroids and provide our first look at these classes of bodies

An asteroid sample return mission to provide samples of primative materials that likely have not survived entry into the Earth's atmosphere to be included in our collection of meteors. (The Marco Polo mission to return samples from an asteroid is in competition for selection ESA's next medium class (300 euro) and would be implemented jointly with the Japanese space agency (JAXA). )

Marco Polo Mission

The multitude of missions to these bodies in the past and in flight raises the bar for future missions. Simple flybys seem unlikely (unless to a very distant object such a Centaur or en route to another destination). Simply orbiting or rendezvousing with a body also seems to be a repeat of past missions and hence would seem unlikely to receive funding. (As a scientist, I like repeating measurements in different places because that allows us to learn about the processes that create similarity and variance. However, doing this with multi-hundred dollar (or euro or rubble or equivalent in your favorite currency) doesn't seem to get your proposal funded.)

While the bar has been raised, there doesn't seem to be any shortage of ideas for future missions to small bodies. The concepts that I have seen discussed include:

Small missions (Discovery class). Proposals and concepts here include missions that would orbit and then land on small bodies (often with several landings). Examples include the Ilion mission to a Trojan asteroid and the CHopper comet redezvous/lander craft. The Deep Interior mission would not land on a comet but would instead orbit it and image its interior in high resolution with surface penetrating radar. A proposal to return samples from several near Earth asteroids was a finalist for the last Discovery selection. Why it wasn't selected isn't known: possible reasons include technical issues, cost concerns, potential science return, or something else. There is also a Discovery mission concept in the works that would collect dust samples at low velocity while flying in formation with a comet and then returning the samples to Earth.

Piecing together hints from various places, it appears that craft that orbit and then land on small bodies could fit within a Discovery budget. A key issue for Discovery class missions is affording a large set of instruments. If you have a craft that observes the body at a distance and on the surface, generally two sets of instruments would seem to be needed. For an asteroid with a rocky surface, one could imagine that the surface instruments could consist of a simple camera, a contact spectrometer for composition, and a robotic arm to place the spectrometer. For a body with significant organics, however, the instrument list for the landing phase becomes more extensive. The proposed instrument list for CHopper, "In addition to high resolution imaging and multi-spectral mappers, the in situ scientific payload instruments under consideration include a dust flux monitor, organic analyzer, elemental analyzer, microscopic imager, and gas mass spectrometer," bears out this argument. As few as two remote sensing instruments and four surface instruments (with the dust flux monitor probably working in both modes). In this case, it might be better to think of the craft as a lander that can also carry out some remote sensing.Medium missions (New Frontiers class). Several studies have suggested that a surface sample could be collected and returned from an asteroid or comet within the budget of a New Frontiers mission (see, for example http://futureplanets.blogspot.com/2009/02/asteroid-sample-return-missions.html and links within that blog post). The Marco Polo mission, once the ESA and JAXA contributions are added together, appears to be in this price range. With sample return missions, we would be get some remote sensing of a body from orbit or rendezvous (the instrument list would probably be short to afford the sample return equipment) and actual samples for detailed analysis in Earth labs.

In general, near Earth asteroids probably would most easily fit within this price range. A study of a comet sample return mission suggested that such a mission might fall into the price range, but with a lot of cavaets (more on that in a moment) See http://www.lpi.usra.edu/opag/nov_2007_meeting/presentations/cssr.pdf for the mission analysis and http://www.lpi.usra.edu/opag/nov_2007_meeting/presentations/cssr_science.pdf for the science rational and goals.Large missions (Flagship). Comets pose a particular challenge for sample return because the desired material to return includes solids (dust, pebbles, etc.) and ices (especially important because we don't have volatile samples from the formation of the solar system). Comet sample return requires that the sample be kept frozen both to preserve water ice (and other ices ideally, but that requires even colder temperatures) and to prevent melting water from chemically altering the solid sample. This cooling requirement apparently pushes comet sample return missions out of the New Frontiers budget at closer to $1B. (See slide 11 in this presentation for a discussion of the budget dilemna: http://www.lpi.usra.edu/sbag/meetings/jan2009/presentations/AHearn_SBAG-EPOXI.pdf). NASA's advisory committees have said that a proposal to return non-cooled samples should be allowed to be submitted for the New Frontiers competitions, but that the proposer will have to justify why the mission can still fulfill the science goals with a warm sample. That sounds like a potential deal breaker that would move comet sample return missions into the large mission class.

My take on all this is that we can expect to continue to see proposals for small body missions in the Discovery program with missions moving to more ambitious goals of landing or carrying out other new types of measurements. I would be surprised if there isn't a proposal for an asteroid sample return mission in the current New Frontiers competition (although we generally learn only of the finalists, not of the proposals that didn't get that far). However, the holy grail of small bodies missions for some time has been to return a large sample from the surface of a comet. It appears that that mission may not fly unless the Decadal Survey in progress makes that mission a high priority for selection as a large mission in the next decade.

The Lunar and Planetary Science conference is one of the big annual conferences in this field. While the conference focuses on results from mission in progress (or past missions), there are always a few stray future mission descriptions or concepts sprinkled in. This year's conference, however, has a wealth of presentations on both. Another nice thing about this conference is that most talks also have substantial (generally two full page) abstracts that provide a lot of detail.

INTERNATIONAL LUNAR NETWORK http://www.lpi.usra.edu/meetings/lpsc2009/pdf/2021.pdf
I believe that this also is an approved NASA mission that would land 4 surface stations on the moon with additional stations for a total of 8-10 provided by other nations. This mission would focus on studies of the lunar interior through seismic, heatflow, electrical conductivity, and rotational dynamics studies.

Moonlite http://www.lpi.usra.edu/meetings/lpsc2009/pdf/1508.pdf
This is a short summary of a mission concept to study many of the same areas as the International Lunar Network but would use high impact penetrators (which would limit payload mass) instead of soft landers.

Venus Flagship http://www.lpi.usra.edu/meetings/lpsc2009/pdf/2410.pdf
A nice (two page) summary of the forthcoming Venus Flagship mission consisting of an orbiter, two balloons, and two landers for a mid-2020's launch. The orbiter would provide data relay from the balloons and landers before settling into a low orbit for high resolution (I've heard elsewhere 5-10 m) radar imaging of a few percent of the surface (much like HiRISE images a small percentage of Mars' surface) and atmospheric studies. The landers would be designed to last for several hours to allow indepth analysis of soil samples.

Mars-Next http://www.lpi.usra.edu/meetings/lpsc2009/pdf/1271.pdf
This would be an ambitious ESA mission to Mars to establish a network of 3-4 landers and an orbiter. The landers would study Mars' interior through seismometry and rotational dynamics studies from radio tracking, atmospheric physics, and studies of the chemistry of rocks and soils. The orbiter would provide data relay and global studies of the atmosphere.

Cerebus (Mars Network) http://www.lpi.usra.edu/meetings/lpsc2009/pdf/2485.pdf
This is a mission that apparently will be proposed for the next NASA New Frontiers selection. Like Mars-Next, this is a network mission with many of the same goals, but without its own orbiter. The mission summary is longer than that for Mars-Next.

Asteroids and Comets

Deep Interior http://www.lpi.usra.edu/meetings/lpsc2009/pdf/2109.pdf
This Discovery mission concept would rendezvous with Wild 2 (which Stardust flew past) and use ground penetrating radar to image the interior structure of a comet at 10 m resolution as well as high resolution imaging of the surface and mapping of the surface topography with a laser altimeter.

MISSION CONCEPTS TO 4015 WILSON-HARRINGTON http://www.lpi.usra.edu/meetings/lpsc2009/pdf/2391.pdf
This small body exhibits characteristics of both an asteroid and a comet. This paper looks at several mission concepts including a Discovery class orbiter/lander and a New Frontiers class sample return mission.

ASIMA (Asteroid Impact Analyzer) http://www.lpi.usra.edu/meetings/lpsc2009/pdf/2305.pdf
This is not a mission in its own right but an instrument that would be added to a low Earth orbit communications satellite. The instrument would study the meteor trails of dust entering the Earth's atmosphere to learn the composition and size of the parent material. Since source of many of the meteors can be traced back to specific comets, this allows a low cost way of studying their composition.

Shotput Sample Return http://www.lpi.usra.edu/meetings/lpsc2009/pdf/1223.pdf
This mission would have a spacecraft flyby a mainbelt, a Trojan, and a Centaur asteroid. At each body, an impactor would strike the target and the spacecraft would fly through the dust plume to sample the surface material. From the mainbelt asteroid, samples of the plume would be collected and returned to Earth during an Earth flyby.

Jupiter and Saturn

Argus (Io) http://www.lpi.usra.edu/meetings/lpsc2009/pdf/1062.pdf
JPL runs a summer school to teach the principles of planetary mission design. Last year's project was to define a New Frontiers mission concept for repeated flybys of Io. This mission would be more capable than the Io Volcano Observer. Forty flybys would be done at 10.6 increments during a two year Io observing campaign. The design assumes design heritage would be available from a Europa Jupiter Flagship mission. Jason Perry has a nice summary of this mission at his blog.

Thursday, February 5, 2009

I'm not one given to finding things cute, but this concept definitely ranks as cute. And possibly quite useful for future planetary missions. It is the Axel Rover jointly developed by JPL and Caltech. It's basically a small cylinder with wheels attached. Cameras, electronics, batteries, etc. are housed inside the cylinder.

This rover won't replace the Mars Science Laboratory or ExoMars. However, it could operate as a nice axillary rover on a mission. As pictured below, it could go to places where a large rover couldn't. Or it could be an adjunct to a network lander. The main station would collect seismometry and weather data while the Axel rover explores the nearby rocks and soils. (Think of it as a round Soujourner.)

I can think of some key limitations (which means t he folks at JPL and Caltech have, too, and probably have better solutions than I'll give.) First, battery life would be limited, and it would seem hard to place a meaningful solar array on the cylinder. However, the tether could supply power from the main rover or lander to recharge the batteries. Second, I'd like a visual-near infrared point spectrometer. And third, I'd like a small second arm t hat would have a contact spectrometer such as an alpha-proton-x-ray spectrometer to measure composition. Just seeing close up pictures of rocks seems to me to be interesting; getting composition too would seem to be to be a dynamite combination. Don't know if you can cram that much in and still keep this rover small, but it's fun to daydream.

Tuesday, February 3, 2009

Along with the selection of the next outer planets Flagship mission, a reoccurring theme of this blog has been candidate missions for the next New Frontiers ($650M not including launcher) mission. (For a list of candidate targets see the poll at the top of the right column.) This entry will deal with the asteroid sample return mission. The science community laid out the case for an asteroid sample return (click here to download the original report; these paragraphs are copied from the text on p. 38 and following):

The primary motivations for an asteroid sample return mission is the desire to both acquire samples with known geologic context and to return materials that are either unlikely to survive passage to Earth (e.g., friable, volatile-rich material) or would be compromised by terrestrial contamination upon their fall (e.g., extraterrestrial organics)...

In the past several years a number of developments have strengthened the case for asteroid sample return. The most important of these is the complete analyses of the data on 433 Eros (Figure 2.8) returned from the NEAR mission and the successful encounter of the Japanese Hayabusa spacecraft with asteroid Itokawa. These encounters demonstrated the diversity of asteroids and their complexity both internally and on the surface. The recognition of the diversity of organics in meteorite samples has prompted a re-evaluation of the astrobiological importance of asteroids.48 A sample return from an organic-rich asteroid may offer insights into the distribution of biogenic compounds and allow an evaluation of whether the delivery of precursor exogenous materials might have contributed to the origin of life...

The decadal survey emphasized the value of a return to asteroid 433 Eros, which has already been the subject of global characterization during the Near Earth Asteroid Rendezvous (NEAR) mission that ended in early 2001. The NEAR mission emphasized the complexity of asteroidal regolith and the need to understand surface processes if remotely sensed spectra of asteroids are to be interpreted...

The committee recommends that although the Asteroid Rover/Sample Return mission should be included as a candidate mission for the New Frontiers Program, the mission objectives should be changed to reflect new scientific information acquired since the decadal survey. Specifically, the unique scientific value of organic-rich targets may elevate them for consideration when compared to the type of asteroid visited by the NEAR mission emphasized by the decadal survey. Such a mission should have the following science objectives, which are not prioritized:

- Map the surface texture, spectral properties (e.g., color, albedo), and geochemistry of the surface of an asteroid at sufficient spatial resolution to resolve geologic features (e.g., craters, fractures, lithologic units) necessary to decipher the geologic history of the asteroid and provide context for returned samples.

- Document the regolith at the sampling site in situ with emphasis on, e.g., lateral and vertical textural, mineralogical, and geochemical heterogeneity at scales down to the submillimeter.

- Return a sample to Earth in an amount sufficient for molecular (or organic) and mineralogical analyses, including documentation of possible sources of contamination throughout the collection, return, and curation phases of the mission.

Conceptual asteroid sample return craft. The large circular object is the solar array. The small disk is the antenna.

What isn't clear from the report is whether near Earth asteroids are likely to have significant organic content. (I have no idea one way or another.) It may be that to acquire pristine organic samples that a sample return from a main belt asteroid would be needed. (If any of the readers of this blog know, please leave a comment.)

At the recent Small Bodies Assessment Group (SBAG), a NASA advisory board, advances in electric propulsion were presented. The presentation included a short summary of a possible mission to return sample from two near Earth asteroids. The key slides are reproduced below. (Click on the image for larger versions or go here for the original presentation.) It appears from the presentation that this class of mission could fit into the New Frontiers budget. There's no data on whether or not a main belt asteroid sample return would, but (editorial comment) I have my doubts. The main belt is further away and the temptation to sample a larger asteroid with a bigger gravity field may bump that mission out of the New Frontiers class.

About Me

You can contact me at futureplanets1@gmail.com with any questions or comments.
I have followed planetary exploration since I opened my newspaper in 1976 and saw the first photo from the surface of Mars. The challenges of conceiving and designing planetary missions has always fascinated me. I don't have any formal tie to NASA or planetary exploration (although I use data from NASA's Earth science missions in my professional work as an ecologist).
Corrections and additions always welcome.